Conventional pneumatic tools, such as a pneumatic wrench, sander or grinder, typically include a motor comprised of a rotor mounted on ball bearings supported by front and rear end plates, positioned on each end of a cylinder, for rotation of the rotor within the cylinder. The rotor and cylinder are non-concentrically aligned to provide a chamber along the length of one side of the rotor for receiving pressurized fluid. The motor is further enclosed within the tool housing. The rotor is slotted lengthwise in a number of equidistant locations about its circumference to support vanes that radially slide in the slots enabling consistent contact between the vane and the inside cylinder wall as the vanes enter and exit the chambered area. Each time a vane enters the chamber, it receives a flow of pressurized fluid passing through the cylinder from the housing and thereby causing the rotor to rotate within the motor and tool housing. Gear teeth on the rotor's shaft transmit rotational force to the working end of the tool.
U.S. Pat. No. 4,678,922 (Leininger) discloses a system for generating electricity using the flow of pressurized fluid such as air in a pneumatic tool by way of a magnetic coupling between a specially designed rotor and a stator. Magnetic means are affixed to the tool rotor, and thereby cooperate during rotation with a stator mounted in the tool housing, motor cylinder or bearing end plate to induce electrical current in the coils of the stator. The '922 disclosure thus provides an integrated, self-contained and self-powered lighting source for illuminating a workpiece. Various improvements have been made to integrated electricity generators in order to improve their electrical output, longevity, usability and efficiency, and also to reduce their size. Examples of such improvements may be found in U.S. Pat. No. 5,525,842 (also to Leininger) in which various configurations of rotor, stator and light supplies are introduced.
Rotors manufactured for use in conventional pneumatic tools are typically machined from steel alloys as a single piece that can be hardened to acceptable standards by heat-treating after machining. Hardening is generally required especially for the pinion area on the rotor shaft because of the rigors undertaken by gear teeth during use of the tool. The drive gear and vane slots in a pneumatic tool rotor are typically machined prior to heat treatment, while the metal is relatively ductile.
When providing a conventional pneumatic tool such as an air tool with electricity generation capabilities, a special rotor appended to a nonmagnetic extension for housing magnets replaces the conventional rotor. The nonmagnetic extension is used to help enhance polar distinction between north and south magnet orientations and to isolate or magnetically insulate magnets as much as possible from the ferromagnetic influences of the steel rotor within the air chamber of a steel air cylinder, and any other magnetic influences in or outside the tool that could interfere with the focus of flux against stator windings.
Because it is difficult to cut down a heat-treated rotor in order to add magnets and a nonmagnetic extension (made of, for instance, nonmagnetic zinc, 300 series stainless steel or aluminum), a special steel rotor having a shortened rotor body is turned, slotted, drilled, hobbed and heat treated and the nonmagnetic extension and magnets are subsequently appended to the rotor body. In an alternative method, a new shaft is machined and heat treated, and subsequently received by a new and nonmagnetic rotor body in which magnets may themselves be received.
As would be understood by one of ordinary skill in the art, machining a special rotor in order to accommodate magnets for inducing electricity in a stator can be complex, time-consuming and accordingly expensive. Furthermore, a manufacturer intent on providing both conventional and electricity-generating models of a particular pneumatic tool must plan for very different methods of manufacture of corresponding rotors.
Conventional pneumatic tools offered by various manufacturers have varying proprietary sizes, shapes, tolerances, operation parameters and the like. As such, each manufacturers' tool also requires a unique stator to generate electricity efficiently and effectively for that tool. Furthermore, pneumatic tools having electricity generating capabilities typically require different magnet-side end plates from their conventional counterparts because of the need to accommodate the size and shape of stator coils and possible supporting circuitry. In addition, size and shape of the tool itself place constraints on the number of windings used for stator coils, the physical placement of supporting circuitry, and location of a pathway for directing generated electricity to its intended load. As would be understood, stator core permeability, size of coils and amount of magnetic interference each factor into the amount of EMF produced by a generator, while considerations such as component cost, manufacturability and degree of variation from a conventional counterpart all contribute to the overall cost of the tool.
Thus, improvements in the manufacturability of tools incorporating such electricity generators are sought.